Design and installation of medical compressed air pipeline system Chen Yuelong, Li Hongyu, Luo Yi (Southern Hospital, First Military Medical University, Guangzhou 510515, China) Abstract: This paper introduces the advantages and disadvantages of medical compressed air centralized supply system and dispersion system. It analyzes and solves a series of problems in system design and installation, such as system safety, air flow, flow rate, quality requirements, and measures to reduce airflow pressure loss in the pipeline. And introduced the test and test methods of the pipeline.
[Key words] Medical compressed air pressure loss pipeline system design Medical compressed air is mainly used for dental diagnosis and treatment equipment, hyperbaric oxygen chamber, ventilator, surgical tower and other equipment. It is very important to design a compressed air distribution system. Only a good compressed air distribution system can provide clean, adequate flow and pressure of compressed air to the above medical equipment, as well as saving power. At present, there are two main types of compressed air distribution systems in hospitals, namely, centralized supply systems and decentralized systems.
1 Centralized supply system The compressed air sent by the main pipeline of the central compressed air station is sent to each user unit through each branch pipe. In hospitals with air-pressed treatment cabins, central compressed air stations are generally considered by the compressed air system of the Hyperbaric Oxygen Therapy.
The centralized supply system has the following advantages and disadvantages: (1) saving the number of air compressors, reducing the noise source, improving the medical environment (2) supplying compressed air at any time, and reducing the manpower and management due to the concentration of the air compressor (3) The air duct is long, the air flow rate in the system will decrease, and the pressure drop will increase (4) the pipeline material and installation cost are high.
2 Dispersion system Dispersion system is that each user unit sets a compressed air supply system according to the needs of its own equipment.
The dispersion system has the following advantages and disadvantages: (1) Compressed air is provided near the gas point, so the pipeline is shorter, reducing the pressure loss (2) the gas source is independent. When adjusting or repairing the system, it has no effect on the gas consumption of the whole hospital. (3) The pipeline material and installation cost are low. (4) For the whole hospital, the number of air compressors increases, resulting in an increase in noise sources, which is not conducive to the medical environment. It is also not easy to manage.
3 Design and installation of pipelines Whether setting up a centralized supply system or setting up a decentralized system, consideration should be given to reducing the pressure loss of air in the pipeline. That is to say, the resistance of the pipeline should be reduced. The air filter should be provided to provide The clean compressed air piping system should be equipped with a water collector to avoid moisture rust. Pneumatic equipment piping system should also be equipped with safety valves, pressure reducers, pressure gauges, etc.
3.1 Pipe material, pipe selection and installation Maintenance pipe types are many, the material can be carbon steel, stainless steel, copper, aluminum and their alloys. The tubes for conveying compressed air are preferably made of stainless steel or non-ferrous materials, but for various reasons of resources and cost, seamless steel tubes made of carbon steel are basically used.
The comprehensive medical equipment information selection pipe must meet the safety requirements of the rated working pressure, and also meet the requirements of a certain flow rate and consider the future expansion. In addition, the rate of airflow in the pipe should be considered to limit the power of the airflow. noise. Excessive flow rates also cause wet air to bypass the drain into the equipment.
The pipe diameter, flow rate and flow rate in the pipeline system have the following relationship: V - volume flow of the pipe, m W - average flow velocity in the pipe, m / s.
The air flow rate in the main pipeline should not exceed 6 m/s. In the branch pipeline not exceeding 15 m, the flow rate is allowed to increase to 15 m/s.
Air filters, safety valves, pressure reducing valves, valves, pressure gauges, etc. should be installed in the piping system. Two safety valves should be installed in important parts to prevent accidents caused by failure of one safety valve.
Whether the pipeline is initially installed or replaced, its work includes surface cleaning of the pipe, pipe laying, automatic thermal compensation of the pipeline, grinding and repair of the valve, verification of the safety valve and pressure gauge, and pressure test of the pipeline. Air tightness test and pipe paint, coloring, etc.
3.2 Measures to reduce the pressure loss of the airflow in the pipeline In order to reduce the pressure loss, the following three measures can be taken (1) to shorten the actual effective stroke of the air, that is, to lay the pipeline should take shortcuts, the shorter the pipeline, the better (2) reduce the airflow blocked The resulting friction (3) reduces the flow rate of air in the system.
Small pipe diameter or long pipe length can increase friction. When establishing a piping system, the pipeline hole requirements should be slightly larger than the actual requirements. With a 25mm tube, the cost is increased by about 50 compared to a 12.5mm tube. However, with equal pressure, the compressed air delivery can be increased by a factor of four.
In the design of the new ward, the main compressed air pipeline should be prioritized relative to other circuits such as circuits and water pipes to ensure the shortest and straightest pipeline. The cost of the main pipeline usually accounts for a considerable proportion of the total cost of installation materials. Although the use of thinner pipelines saves money, the large pressure loss leads to high operating costs, which is actually a small loss.
In order to meet the maximum gas consumption of the gas point without causing significant pressure loss, all bend lines of the system should have sufficient radius. The so-called obvious pressure drop is an empirical value. The pressure loss per pipe of 300m can be about 5, but the farthest pipeline pressure loss should not exceed the place where the gas point is relatively far and the gas consumption is large. The container, such that the air flow rate and its pressure drop in the system will also decrease while the use of this gas storage container to deliver compressed air to the point of use will increase the flow of compressed air in the piping system.
3.3 Pipeline slope and setting of all the air pressure main pipe systems of the water collector from the air compressor shall have a slope of not less than 1, that is, 30 mm per 3 m length. At the same time, water collection shall be provided at the lower part of the pipeline system. The water in the pipeline is concentrated and discharged. All outlet points should be taken from the top of the line to help reduce moisture entering the equipment and compressed air.
The pipes buried in the installation also have slopes, and the drains and wells are set at low points. When the pipeline is affected by temperature changes, for example, from indoors to another building outside, the temperature will decrease. In this case, a water collector should be installed in the room entering another building to remove the condensation. Moisture. To avoid freezing, pipes exposed to cold weather should be fitted with a temperature barrier.
4 Test, blow-off and air tightness test of pipelines For medium and low pressure pipelines, the hydraulic pressure test pressure is equal to 1.25 times of the design pressure, and the high pressure pipeline hydraulic pressure test is performed at 1.5 times the design pressure. When the hydraulic pressure test is carried out, it shall be carried out according to different pressure sub-systems of different process stages, and the instruments and equipment that cannot be used for hydraulic pressure test shall be separated by blind plates. When filling the water, the vent valve at the highest point should be opened, so that the gas exhaust pressure in the system should be slowly raised to the test pressure, the pressure is stopped for 10 minutes, and then the tightness of the weld, flange and valve seal is inspected in detail. The water in the system should be drained after passing the test.
The blowing of the pipeline shall also be carried out in stages according to the system. Pipe fittings and equipment such as filters that are not allowed to be blown shall be removed. When blowing, the board to which the white cloth is attached is placed in the purge section for inspection. When there is no rust or sputum on it, it is considered that the blow is qualified.
The airtightness test was carried out at a design pressure of 1.05 times, and the test was carried out with air or an inert gas. After the pressure is gradually raised to the test pressure, it is checked by brushing soapy water, and no leakage is considered acceptable. Thereafter, the pressure is ramped up to the maximum working pressure of the piping system and the leak test is carried out over several hours.
The leakage rate is calculated according to the following formula: A - the average percentage of leakage per hour, - the pressure at the beginning of the test, M Pa - the pressure at the end of the test, M Pa - the ambient temperature at the beginning of the test, K - the ambient temperature at the end of the test, K t - Test time, h (hours).
Improvement of medical equipment information integrated flame photometer DC voltage regulator circuit Wang Xuewen (Shuikoushan Mining Bureau Staff Hospital Laboratory, Changning, Hunan) HG 3 flame photometer DC voltage regulator circuit uses more discrete components, the circuit is more complicated The stability is not ideal. The author used two T L431 with a small number of RC components to improve the HG 3 flame photometer DC voltage regulator circuit. Figure 1 is the improved circuit schematic diagram, Figure 2 is the TL431 pin function diagram.
The improved circuit schematic TL431 is a cost-effective precision adjustable three-terminal DC voltage regulator integrated circuit, which is widely used in various DC voltage regulator circuits with excellent performance and low price. The main technical parameters are temperature coefficient 50μV/°C (the temperature coefficient of the PN junction of the silicon triode is 100mA, and the voltage regulation effect is excellent.
The operating current of the HG 3 flame photometer DC amplifier is generally not more than 10mA (±12V power supply). The circuit design of Figure 1 has an output current of about 20 mA, which is fully capable of powering the HG 3 flame photometer amplifier.
The stability and reliability of the improved DC voltage regulator circuit are greatly increased, and the zero drift is basically invisible.
When improvement, remove the original DC voltage regulator circuit board, remove the board remover, and solder the TL431 in place. In addition, R is also installed in a suitable place and connected to the original circuit output terminal. Completed, fine-tuning 2W1, 2W2 to make the output ±12V can be used.
Figure 2 TL431 pin function diagram New materials and new devices emerge in an endless stream. It takes several years for the inspection equipment to go from design to production to sales and operation to laboratory applications. There is a time lag problem, and many new technologies and new cost-effective components have been widely used during this period. In addition, the limitations of the designer's knowledge on the imperfections of equipment design also exist. Therefore, inspectors or equipment maintenance personnel are entirely possible and necessary to make full use of this time difference, and use their knowledge to properly modify the local circuits of some conventional equipment to make new functions and performance more perfect. Promising, it is also very real and meaningful.
The leakage rate should meet the requirements of the following table: Test part test pressure (MPa) Leakage rate (/ h) The gas supply line connected to the storage cylinder The maximum working pressure of the piping system is not the gas supply line connected to the storage tank. The maximum working pressure of the piping system References] and Dawen. Medical Hyperbaric Oxygen Engineering and Technology [M]. Chengdu: Chengdu University of Science and Technology Press, 1992.
Medical equipment information research and innovation
Is it Time to Change Your Windshield Wiper Arm?
All windshield wiper arms have a hinge at the base that allows the arm to flex as it follows the curvature of the window. If the wiper skips over certain spots, even with a new blade, chances are the hinge is binding from corrosion. It`s most common on rear window wipers since they`re used less often.
You can oil the hinge, but that`s just a temporary fix-the corrosion and binding usually return. To fix the problem permanently, replace the Wiper Arm (available at an auto parts store).
What you`ll need to replace your windshield wiper arm:
- Socket/ratchet set
- Flat-blade screwdriver
Now you`re ready to get started!
Plug-In Wiper Arm,Rear Window Wiper Arm ,Rear Windscreen Wiper Arm,Front Wiper Arm
COMOTECH ASIA PACIFIC (HANGZHOU)CO.,LTD , http://www.capwiper.com